…until the late 20th century the majority of the ancestry of the white population of the republic descended from those who were counted in the 1790 census.

A commenter questioned the assertion. The commenter was right to question it. My source was a 1992 paper that estimated that only in 1990 did the proportion of American ancestry which derived from those who arrived after the 1790 census exceeding 50%. In other words, if you ran the ancestors of all Americans back to 1790, a majority of that set would have been counted in the 1790 census (so people of mixed ancestry would contribute to the two components are weighted by their ancestry).
The major issue here is that there is a difference between whites, and non-whites, especially before mass Asian and Latin American immigration post-1965, when white vs. non-white ~ white vs. black. Almost all the ancestors of black Americans who were black were already resident in the United States in 1790. A few years ago I read up on the history of American slavery and was surprised how genuinely indigenous the black American, slave and free, population was by the late 18th century (English speaking and Christian). There was an obvious reason why Southern slave-holders went along with the ban on importation of slaves which was due to kick in in the early decades of the republic: American blacks, unlike slave populations elsewhere in the New World, had endogenous natural increase. This explains part of the relative paucity of African aspects in their culture in relation to the blacks of Haiti or Brazil, where African-born individuals were still very substantial numerically at emancipation because of high attrition rates (it is sometimes asserted that the majority of blacks liberated during the Haitian Revolution were born in Africa. Likely a hyperbole, but it gets across the strength of connection).

In any case, to estimate the white proportion attributable to 1790, I have to correct for the black proportion within the total. As an approximation I think it’s acceptable to simply attribute blacks as a whole to the proportion which had ancestors here in 1790 in full. I suspect a greater proportion of the black ancestry which post-dates 1790 would come from the white component of their heritage which simply isn’t of notice in American society for various reasons in any case (Henry Louis Gates Jr. is more white than he is black in terms of ancestry, but he’s the doyen of Africana Studies). So, assuming that blacks contribute to the 1790 and before component in full, I estimate that between 1910 and 1920 the majority of the ancestry of the white population shifted from 1790 and before, to after. Specifically, in 1910 51% of the ancestry could be traced to 1790 and before among whites, and in 1920 49%. In 1950 it was 47% 1790 and before. So I should have said early 20th century, not late. I wouldn’t be surprised though if the balance has started to shift in recent years, as many “white ethnic” groups (Jews, Italians, Irish, etc.) are more heavily concentrated in urban areas, while the most fertile white community in the United States, the Mormons of Utah, are also the most Old Stock Yankee in ancestry (I am aware that many Mormons are descended from European immigrants who converted in Europe and made the journey after conversion, but Mormons are still far more Old Stock Yankee than any group outside of interior New England).

http://haquelebac.wordpress.com/2010/04/06/my-fossil-railroad/ John Emerson

The slave trade (importing) continued until 1808, though I don’t know the numbers.

Does your number mean that 50%+ of the total number of ancestors of Americans alive in 1790 were already in the U.S.? As of 1840 or so my ancestors are 5/8 immigrant and 3/8 old stock, and that number carries backward to 1790. So I would could as something like 5/8 – 3/8?

http://haquelebac.wordpress.com/2010/04/06/my-fossil-railroad/ John Emerson

“I would COUNT as something like 5/8 – 3/8?”

http://blogs.discovermagazine.com/gnxp Razib Khan

I would COUNT as something like 5/8 – 3/8

yeah. some ancestors would show up twice or three times (especially older ones), so i think that’s accounted for. it makes more sense to just talk about genetic content, but this was 1992 so it used older genealogical terminology.

as for the slave trade, yes. but from what i have read the overwhelming majority of the ancestors of black americans were already around by 1790. the northern southern states like virginia actually shifted to a slave-breeding economy to complement the new south states where massive expansion of cotton growing was occurring. black american/slave growth rates were much slower than white because of the conditions, but in contrast all other new world slave populations they were above replacement. probably a condition of land surplus, lower disease load, as well as the fact the crops in north america, cotton and tobacco, weren’t as ameas for the slave trade, yes. but from what i have read the overwhelming majority of the ancestors of black americans were already around by 1790. the northern southern states like virginia actually shifted to a slave-breeding economy to complement the new south states where massive expansion of cotton growing was occurring. black american/slave growth rates were much slower than white because of the conditions, but in contrast all other new world slave populations they were above replacement. probably a condition of land surplus, lower disease load, as well as the fact that cotton and tobacco weren’t as amenable to industrial scalability as sugar. it was more economy efficient in the sugar economies to simply work a slave to death over a few years, and replace them, than in regards to north american cash crops which required a little more skill.

http://blogs.discovermagazine.com/gnxp Razib Khan

many customs in the black american community turn out to be scots-irish. there is some suspicion that they picked these up during a period when race relations weren’t as polarized and poor indentured whites worked along with blacks. e.g., jumping over the broom at a wedding is a celtic custom.

bioIgnoramus

What proportion of the whites were descended from the criminals sent to the North American colonies before independence meant that New South Wales had to be developed as an alternative?

http://blogs.discovermagazine.com/gnxp Razib Khan

don’t know. i know the other colonists hated them and complained about them. probably varies by region, i doubt they could have made a go of it in new england because of the communitarian aspects of that region made it hard for outsiders to manage to stick around. i doubt that many because the base population of the colonies was already way higher than australia was for a long time.

Only about 50% of the Mormons present in Nauvoo at the death of Joseph Smith migrated to Utah and European converts were disproportionately represented in this group, as many had loyalties to the Brighamite Quorum of the Twelve, who had converted most of them and arranged their passage to the United States.

At one time, the population of the Utah territory was nearly 50% European-born. My own ancestry mirrors this division. About half can be traced to pre-1700 New England stock, and the other half is English, Scottish, Danish, and Swedish converts from 1840-1857.

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About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com